Rotation Periods

RPM
I browsed around for typical rotation periods for the radars of interest. What is common among Furuno and Raytheon are the values in RPM:

• 24 rpm
• 36 rpm
• 48 rpm

This is an interval of 20 to 50 rpm which is equivalent to a 1.5 to 2.5 second period. This will be very useful in designing a bandpass type filter that will allow us to ignore unwanted periodic signals.

Periodic Measurement
There are at least two methods of measuring the period.

1. Grab a horizontal slice and match it with another frame X frames later. Do this for several slices to get a large sample size. Measure the average. This method may be a very simplified version of what Cutler and Davis do. I will need to read their paper.
   
2. Measure the harmonic signals within the "helix" shape using 1D signal processing and resolve the period value.